The multiple occurrences of SLE over several generations in families suggest the importance of genetic factors in SLE pathogenesis. In this project, alloantigens on B-lymphocytes, coded for by genes on the sixth chromosome known as the major histocompatibility complex, will be examined in patients with SLE. Select families with multiple occurrences of SLE will also be studied. These alloantigens have physico-chemical and amino acid sequence homologies with murine B-cell antigens responsible for the regulation of specific immune responses. The frequency of individual alloantigens in SLE, as compared to normal controls, will be used in an attempt to identify immune genetic markers associated with SLE.